1. Field Of The Invention
The present invention relates to electrical connectors, and more particularly to connectors for terminating or otherwise making electrical contact with thin, flat, flexible conductor circuit elements, commonly referred to as a "flex circuit" and having a plurality of ribbons of conductive material. Such a connector should provide reliable electrical contact and sufficient mechanical support or strain relief to further insure circuit continuity. This connector typically interfaces a flat flexible conductor with a printed circuit or other circuit board, but is equally suitable for connection with another flexible circuit or wires. Preferably, such a connector should have a zero insertion force to avoid damage to the thin flexible circuit, such as scratching, scarring, or galling.
2. Brief Description Of The Prior Art
Flexible circuits and flat multi-conductors are well known in the art and are commonly used because of their reliability, flexibility, compactness, and ability to satisfy unusual space restrictions.
In the past, flexible circuits have been connected to other circuit elements by, among other methods, soldering. This has the disadvantages of being costly in time and equipment, and requiring special tools and materials such as soldering irons, flux, solder, and cleaning solutions. This method requires considerable caution and skill to avoid improper or "cold" connections and runs a substantial risk of heat damage to the flexible circuit and other circuit elements. Disconnection is often messy, self-defeating, and runs the same risks, in addition to being equally costly.
Other methods of connection include bonding, crimping, pressure contact, and welding. While the first three may not result in heat damage, physical damage may result from the required deformation of the circuit elements or conductors, and the reliability is often unacceptably low. Welding requires specially designed equipment, skilled personnel, and significant amounts of heat, thereby suffering from many of the disadvantages of soldering.
Known pressure connectors suffer a host of disadvantages or disabilities. U.S. Pat. No. 3,090,028, issued to Hall et al., discloses a pressure connector requiring close manufacturing tolerances for a proper fit between successive partition and presser members. It is necessary to undertake an exact and complex partial stripping of the cable insulation for proper contact, and then slit the conductor substrate between each connector for depression into the contact wells when the cover is closed. This likely requires special tools and training, and may result in damaged or misaligned conductors. Further, once the conductor is slit and stripped, it will not be compatible with other connectors. Another connector requiring close manufacturing tolerances and complex molds is U.S. Pat. No. 3,989,336, issued to Rizzio et al., which discloses a pressure connector requiring intricate and pre-loaded contact loops. Strain relief is provided for the movable cover, which suffers from plastic cold-flow deformation problems, and an upward pull on the conductor may disengage the cover and open the connector. Other strain relief is provided, but it requires delicate threading around sharp corners which may break the narrow conductive strips. The design requires that the housing define an opening into which the conductor must be inserted. There is no visual indication of when the conductor is properly seated and the connector may only be mounted on one side. Use is further complicated and practically restricted to circuit boards because the connecting end of the contacts and the flex circuit are disposed on the same side of the connector, it is difficult to maintain electrical isolation. Said conductor, as well as the one disclosed by Hall et al., also lacks provisions for through connection.
Still other pressure connectors, such as that disclosed in U.S. Pat. No. 3,307,139, issued to Prise, are "sandwich" connectors for connecting two flex cables. Such are not compatible for connection with circuit boards or other conductors.
A more recent method is to use an edge connector similar to those for connecting rigid circuit boards or elements. Although these have been successful with rigid connectors, they require the application of an insertion force, which is often incompatible with or may result in irreparable damage to a flexible circuit.